Add the incremental option

[pcav]

See e.g. man pandoc

   -i, --incremental
          Make list items in slide shows  display  incrementally  (one  by
          one).  The default is for lists to be displayed all at once.

[marianoguerra]

do you want to apply to all the items in all slides?

[pcav]

IMHO it would be good to follow the

.. incremental::

directive in the slides where it is present, and apply it to the items following it, until the end of the slide.

[pcav]

I mean:

.. class:: incremental